Fix uninitialized read of CalleeWithThisReturn.

Initialize CalleeWithThisReturn to 0 in the constructor.
Also revert r170815 since checking CalleeWithThisReturn is faster.

PR15598


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178053 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 473a1cb..2c3cabe 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -42,7 +42,8 @@
     AutoreleaseResult(false), BlockInfo(0), BlockPointer(0),
     LambdaThisCaptureField(0), NormalCleanupDest(0), NextCleanupDestIndex(1),
     FirstBlockInfo(0), EHResumeBlock(0), ExceptionSlot(0), EHSelectorSlot(0),
-    DebugInfo(0), DisableDebugInfo(false), DidCallStackSave(false),
+    DebugInfo(0), DisableDebugInfo(false), CalleeWithThisReturn(0),
+    DidCallStackSave(false),
     IndirectBranch(0), SwitchInsn(0), CaseRangeBlock(0), UnreachableBlock(0),
     CXXABIThisDecl(0), CXXABIThisValue(0), CXXThisValue(0),
     CXXStructorImplicitParamDecl(0), CXXStructorImplicitParamValue(0),